Chiang Kai-shek (October 31, 1887 – April 5, 1975) was a Chinese political and military leader who served as the leader of the Republic of China between 1928 and 1975. He is known as Chiang Chung-cheng (蔣中正, Jiǎng Zhōngzhèng) or Chiang Chieh-shih (蔣介石, Jiǎng Jièshí) in Standard Chinese. Chiang was an influential member of the Kuomintang (KMT), the Chinese Nationalist Party, and was a close ally of Sun Yat-sen. He became the Commandant of the Kuomintang's Whampoa Military Academy and took Sun's place as leader of the KMT when Sun died in 1925. In 1926, Chiang led the Northern Expedition to unify the country, becoming China's nominal leader. He served as Chairman of the National Military Council of the Nationalist government of the Republic of China (ROC) from 1928 to 1948. Chiang led China in the Second Sino-Japanese War (the Chinese theater of World War II), consolidating power from the party's former regional warlords. Unlike Sun Yat-sen, Chiang Kai-shek was socially conservative, promoting traditional Chinese culture in the New Life Movement and rejecting western democracy and the nationalist democratic socialism that Sun embraced in favour of an authoritarian government.